Multi-channel wireless communications

ABSTRACT

Systems and techniques relating to wireless communications are described. A described technique includes monitoring wireless communication channels, including a first channel and a second channel, to produce a monitoring output, determining a first transmission period for the first channel, determining a second transmission period for the second channel, transmitting, based on the first transmission period, a first packet on the first channel to cause one or more wireless communication devices to set a transmission protection period for the first channel and the second channel based on a reception of the first packet, transmitting, based on the second transmission period, a second packet on the second channel, and monitoring, after the end of the first transmission period, for one or more acknowledgements. An end of the second transmission period can be aligned with an end of the first transmission period.

CROSS REFERENCE TO RELATED APPLICATIONS

This disclosure claims the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/329,905, filed Apr. 30, 2010 and entitled “11acMulti-Channel Support”; the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/316,268, filed Mar. 22, 2010 and entitled “11acMulti-Channel Support”; the benefit of the priority of U.S. ProvisionalApplication Ser. No. 61/312,135, filed Mar. 9, 2010 and entitled “11acMulti-Channel Support”; and the benefit of the priority of U.S.Provisional Application Ser. No. 61/261,108, filed Nov. 13, 2009 andentitled “11ac Band Support.” All of the above identified applicationsare incorporated herein by reference in their entirety.

BACKGROUND

This disclosure relates to wireless communication systems, such asWireless Local Area Networks (WLANs).

Wireless communication systems can include multiple wirelesscommunication devices that communicate over one or more wirelesschannels. When operating in an infrastructure mode, a wirelesscommunication device called an access point (AP) provides connectivitywith a network, such as the Internet, to other wireless communicationdevices, e.g., client stations or access terminals (AT). Variousexamples of wireless communication devices include mobile phones, smartphones, wireless routers, and wireless hubs. In some cases, wirelesscommunication electronics are integrated with data processing equipmentsuch as laptops, personal digital assistants, and computers.

Wireless communication systems, such as WLANs, can use one or morewireless communication technologies, such as orthogonal frequencydivision multiplexing (OFDM). In an OFDM based wireless communicationsystem, a data stream is split into multiple data substreams. Such datasubstreams are sent over different OFDM subcarriers, which can bereferred to as tones or frequency tones. WLANs such as those defined inthe Institute of Electrical and Electronics Engineers (IEEE) wirelesscommunications standards, e.g., IEEE 802.11a, IEEE 802.11n, or IEEE802.11ac, can use OFDM to transmit and receive signals.

Wireless communication devices in a WLAN can use one or more protocolsfor medium access control (MAC) and physical (PHY) layers. For example,a wireless communication device can use a Carrier Sense Multiple Access(CSMA) with Collision Avoidance (CA) based protocol for a MAC layer andOFDM for the PHY layer.

Some wireless communication systems use a single-in-single-out (SISO)communication approach, where each wireless communication device uses asingle antenna. Other wireless communication systems use amultiple-in-multiple-out (MIMO) communication approach, where a wirelesscommunication device, for example, uses multiple transmit antennas andmultiple receive antennas. A MIMO-based wireless communication devicecan transmit and receive multiple spatial streams over multiple antennasin each of the tones of an OFDM signal.

SUMMARY

The present disclosure includes systems and techniques for wirelesscommunications.

According to an aspect of the present disclosure, a technique forwireless communications includes monitoring wireless communicationchannels, including a first channel and a second channel, to produce amonitoring output, determining a first transmission period for the firstchannel based on the monitoring output, determining a secondtransmission period for the second channel based on the monitoringoutput, transmitting, based on the first transmission period, a firstpacket on the first channel to cause one or more wireless communicationdevices to set a transmission protection period for the first channeland the second channel based on a reception of the first packet,transmitting, based on the second transmission period, a second packeton the second channel, and monitoring, after the end of the firsttransmission period, for one or more acknowledgements. Determining afirst transmission period for the first channel can include applying afirst inter-packet duration and a second inter-packet duration to themonitoring output, where the second duration is shorter than the firstduration. Determining a second transmission period for the secondchannel can include applying a first inter-packet duration, a secondinter-packet duration, or a combination thereof to the monitoringoutput. An end of the second transmission period can be aligned with anend of the first transmission period.

According to an aspect of the present disclosure, a technique forwireless communications includes monitoring wireless communicationchannels, including a first channel and a second channel, to produce amonitoring output, determining a first transmission period for the firstchannel by applying a first Interframe Space (IFS) duration and a secondIFS duration to the monitoring output, wherein the second duration isshorter than the first duration, determining a second transmissionperiod for the second channel by applying the first IFS duration and thesecond IFS duration to the monitoring output, transmitting, based on thefirst transmission period, a first packet on the first channel to causeone or more wireless communication devices to set a transmissionprotection period for the first channel and the second channel based ona reception of the first packet, transmitting, based on the secondtransmission period, a second packet on the second channel, andmonitoring, after the end of the first transmission period, for one ormore acknowledgements. An end of the second transmission period can bealigned with an end of the first transmission period.

The described systems and techniques can be implemented in electroniccircuitry, computer hardware, firmware, software, or in combinations ofthem, such as the structural means disclosed in this specification andstructural equivalents thereof. This can include at least onecomputer-readable medium embodying a program operable to cause one ormore data processing apparatus (e.g., a signal processing deviceincluding a programmable processor) to perform operations described.Thus, program implementations can be realized from a disclosed method,system, or apparatus, and apparatus implementations can be realized froma disclosed system, computer-readable medium, or method. Similarly,method implementations can be realized from a disclosed system,computer-readable medium, or apparatus, and system implementations canbe realized from a disclosed method, computer-readable medium, orapparatus.

For example, one or more disclosed embodiments can be implemented invarious systems and apparatus, including, but not limited to, a specialpurpose data processing apparatus (e.g., a wireless communication devicesuch as a wireless access point, a remote environment monitor, a router,a switch, a computer system component, a medium access unit), a mobiledata processing apparatus (e.g., a wireless client, a cellulartelephone, a smart phone, a personal digital assistant (FDA), a mobilecomputer, a digital camera), a general purpose data processing apparatussuch as a computer, or combinations of these.

Systems and apparatuses can include processor electronics configured tomonitor wireless communication channels, including a first channel and asecond channel, to produce a monitoring output, determine a firsttransmission period for the first channel by applying a first IFSduration and a second IFS duration to the monitoring output, wherein thesecond duration is shorter than the first duration, determine a secondtransmission period for the second channel by applying the first IFSduration and the second IFS duration to the monitoring output, control atransmission, based on the first transmission period, of a first packeton the first channel to cause one or more wireless communication devicesto set a transmission protection period for the first channel and thesecond channel based on a reception of the first packet, control atransmission, based on the second transmission period, a second packeton the second channel, and monitor, after the end of the firsttransmission period, for one or more acknowledgements.

These and other implementations can include one or more of the followingfeatures. Implementations can include circuitry to transmit and receiveon wireless communication channels. Implementations can includecircuitry to access wireless communication channels, which can includecircuitry to receive samples from an analog-to-digital convertor andcircuitry to send data to a digital-to-analog convertor. In someimplementations, the first duration is an Arbitration IFS (AIFS)duration. In some implementations, the second duration is a PointCoordination Function IFS (PIFS) duration. In some implementations, theprocessor electronics are configured to monitor for wireless traffic onthe wireless communication channels with respect to the first durationand the second duration. The processor electronics, in response to themonitoring output indicating a presence of traffic on the first channelduring a period based on the AIFS duration, can be configured todetermine the first transmission period based on an end of the PIFSduration. The processor electronics, in response to the monitoringoutput indicating a presence of traffic on the second channel during aperiod based on the AIFS duration, can be configured to determine thesecond transmission period based on an end of the PIFS duration. In somecases, the first packet is transmitted to a first wireless communicationdevice that is configured for communications based on a first wirelesscommunication standard, and the second packet is transmitted to a secondwireless device that is configured for communications based on a secondwireless communication standard, where the first channel is used by eachof the first wireless communication standard and the second wirelesscommunication standard. In some implementations, the first packetincludes a field indicative of a length of the first packet. In someimplementations, the processor electronics are configured to set thefield to indicate a downlink Orthogonal Frequency-Division MultipleAccess transmission. In some implementations, the first packet and thesecond packet are transmitted to the same wireless communication device,and the wireless communication channels are associated with anoverlapping basic service set (OBSS) configured for communications basedon 80 MHz, 120 MHz, or 160 MHz bandwidths.

Details of one or more implementations are set forth in the accompanyingdrawings and the description below. Other features and advantages may beapparent from the description and drawings, and from the claims.

DRAWING DESCRIPTIONS

FIG. 1 shows an example of a channel structure for wirelesscommunications.

FIG. 2 shows an example of a wireless network with two wirelesscommunication devices.

FIG. 3 shows an example of a wireless communication device architecture.

FIG. 4 shows an example of a communication process for multi-channelwireless communications.

FIGS. 5A, 5B, 5C, and 5D show different examples of communication flowsvia multiple channels.

FIG. 6 shows an example of a bandwidth indication for downlinkOrthogonal Frequency-Division Multiple Access (OFDMA).

FIGS. 7A and 7B show examples of communication flow layouts, includingacknowledgement responses, based on Orthogonal Frequency-DivisionMultiple Access (OFDMA).

FIG. 8 shows an example of a communication flow layout for a primarychannel and four secondary channels.

FIG. 9 shows an example of a dual-primary channel structurearchitecture.

FIG. 10 shows an example of a layout of overlapping channelizations.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure provides details and examples of technologies forwireless local area networks, including systems and techniques formulti-channel wireless communications. An example of a technique formulti-channel device wireless communications includes operating awireless communication device to communicate with two or more differenttypes of wireless communication devices in a way that increasesbandwidth utilization. Potential advantages include an increasedutilization of primary and secondary channel bandwidth, backwardscompatibility with older standards, or both. The techniques andarchitectures presented herein can be implemented in a variety ofwireless communication systems such as ones based on IEEE 802.11ac.

FIG. 1 shows an example of a channel structure for wirelesscommunications. Wireless communication devices 105, 110, 115 cancommunicate over a group 120 of channels 125, 130, 135, 140, which caneach be 20 megahertz (MHz) wide. The group 120 can be in an 80 MHzoverlapping basic service set (OBSS) configuration. The group 120includes two primary channels 125, 135 (referred to as P1 and P2,respectively) and associated secondary channels 130, 140 (referred to asS1 and S2, respectively).

A transmission on the P1 channel 125 sets a transmission protectionperiod such as a network allocation vector (NAV) on channels associatedwith the group 120. An AP device 105 can communicate with differenttypes of devices (e.g., devices based on different standards) such as ahigh-throughout (HT) device 110 (e.g., IEEE 802.11n based device) and avery high-throughout (VHT) device 115 (e.g., IEEE 802.11ac baseddevice). A HT device 110 is configured to use the P1 channel 125, the S1channel 130, or a combination of these, whereas the VHT device 115 isconfigured to use the P1 channel 125, the P2 channel 135, the S1 channel130, the S2 channel 140, or a combination of two or more of thesechannels. The AP can concurrently transmit to the VHT device 115 and theHT device 110.

In some cases, an AP device 105 transmits to the VHT device 115 using aP2 channel 135 and transmits to the HT device 110 using a P1 channel125. The AP device 105 coordinates the transmission of one or morepackets on the P1 and P2 channels 125, 135 such that they end at thesame time to create a window for acknowledgements (ACKs). Moreover, anAP device 105 can use the P1 channel 125 and the S1 channel 130 toprovide a 40 MHz wide transmission to a HT device 110 and use the P2channel 135 and the S2 channel 140 to provide a 40 MHz wide transmissionto a VHT device 115. In some cases, the AP can use all of the channelsof the group 120 to communicate with a single device.

FIG. 2 shows an example of a wireless network with two wirelesscommunication devices. Wireless communication devices 205, 207 such asan access point (AP), base station (BS), wireless headset, accessterminal (AT), client station, or mobile station (MS) can includecircuitry such as processor electronics 210, 212. Processor electronics210, 212 can include one or more processors that implement one or moretechniques presented in this disclosure. Wireless communication devices205, 207 include circuitry such as transceiver electronics 215, 217 tosend and receive wireless signals over one or more antennas 220 a, 220b, 222 a, 222 b. In some implementations, transceiver electronics 215,217 include integrated transmitting and receiving circuitry. In someimplementations, transceiver electronics 215, 217 include multiple radiounits. In some implementations, a radio unit includes a baseband unit(BBU) and a radio frequency unit (RFU) to transmit and receive signals.Transceiver electronics 215, 217 can include one or more of: detector,decoder, modulator, and encoder. Transceiver electronics 215, 217 caninclude one or more analog circuits. Wireless communication devices 205,207 include one or more memories 225, 227 configured to storeinformation such as data, instructions, or both. In someimplementations, wireless communication devices 205, 207 includededicated circuitry for transmitting and dedicated circuitry forreceiving. In some implementations, a wireless communication device 205,207 is operable to act as a serving device (e.g., an access point), or aclient device.

In some implementations, a first wireless communication device 205 cantransmit data to one or more devices via two or more spatial wirelesscommunication channels such as orthogonal spatial subspaces, e.g.,orthogonal Space Division Multiple Access (SDMA) subspaces. For example,the first wireless communication device 205 can concurrently transmitdata to a second wireless communication device 207 using a spatialwireless channel and can transmit data to a third wireless communicationdevice (not shown) using a different spatial wireless channel. In someimplementations, the first wireless communication device 205 implementsa space division technique to transmit data to two or more wirelesscommunication devices using two or more spatial multiplexing matrices toprovide spatially separated wireless channels in a single frequencyrange.

Wireless communication devices, such as a MIMO enabled access point, cantransmit signals for multiple client wireless communication devices atthe same time in the same frequency range by applying one or moretransmitter side beam forming matrices to spatially separate signalsassociated with different client wireless communication devices. Basedon different signal patterns at the different antennas of the wirelesscommunication devices, each client wireless communication device candiscern its own signal. A MIMO enabled access point can participate insounding to obtain channel state information for each of the clientwireless communication devices. The access point can compute spatialmultiplexing matrices, such as spatial steering matrices, based on thedifferent channel state information to spatially separate signals todifferent client devices.

FIG. 3 shows an example of a wireless communication device architecture,which can include the various implementation details described above. Awireless communication device 350 can produce signals for two or moreclients in two or more frequency ranges. Note that a channel can beassociated with a frequency range. A frequency range can include a groupof OFDM sub-carriers. The wireless communication device 350 includes aMAC module 355. The MAC module 355 can include one or more MAC controlunits (MCUs) (not shown). The wireless communication device 350 includesthree or more encoders 360 a, 360 b, 360 c that receive data streams,from the MAC module 355, which are associated with one or more clients(e.g. N clients, or N transmission streams to one or more clients). Theencoders 360 a, 360 b, 360 c can perform encoding, such as a forwarderror correction (FEC) encoding technique to produce respective encodedstreams. Modulators 365 a, 365 b, 365 c can perform modulation onrespective encoded streams to produce modulated streams to an OrthogonalFrequency-Division Multiple Access (OFDMA) Inverse Fast FourierTransform (IFFT) module 380.

The OFDMA IFFT (O-IFFT) module 380 can perform IFFTs on modulatedstreams from respective modulators 365 a, 365 b, 365 c. In someimplementations, the O-IFFT module 380 can include an OFDMA module andan IFFT module, where the OFDMA module maps different modulated streamsto different subcarrier groups before IFFT processing. In someimplementations, the O-IFFT module 380 can perform an IFFT on an outputof the first modulator 365 a to produce a first time domain signalassociated with a first frequency range. The O-IFFT module 380 canperform an IFFT on an output of the second modulator 365 b to produce asecond time domain signal associated with a second frequency range. TheO-IFTT module 380 can perform an IFFT on an output of the Nth modulator365 c to produce an Nth time domain signal associated with an Nthfrequency range.

In some implementations, the O-IFFT module 380 can combine the frequencycomponents, e.g., frequency range components, associated with the outputof respective first modulators 365 a, 365 b, 365 c. The O-IFFT module380 can perform an IFFT on the combination to produce a time domainsignal associated with the frequency ranges. In some implementations, anO-IFFT module 380 is configured to use one or more FFT bandwidthfrequencies, e.g., 20 MHz, 40 MHz, 80 MHz, and 160 MHz. In someimplementations, the O-IFFT module 380 can perform different IFFTs.

A digital filtering and radio module 385 can filter the time domainsignal and amplify the signal for transmission via an antenna module390. An antenna module 390 can include multiple transmit antennas andmultiple receive antennas. In some implementations, an antenna module390 is a detachable unit that is external to a wireless communicationdevice 350.

In some implementations, a wireless communication device 350 includesone or more integrated circuits (ICs). In some implementations, a MACmodule 355 includes one or more ICs. In some implementations, a wirelesscommunication device 350 includes an IC that implements thefunctionality of multiple units and/or modules such as a MAC module,MCU, BBU, or RFU. In some implementations, a wireless communicationdevice 350 includes a host processor that provides a data stream to aMAC module 355 for transmission. In some implementations, a wirelesscommunication device 350 includes a host processor that receives a datastream from the MAC module 355. In some implementations, a hostprocessor includes a MAC module 355.

FIG. 4 shows an example of a communication process for multi-channelwireless communications. At 405, a communication process monitorswireless communication channels, including a first channel and a secondchannel, to produce a monitoring output. The monitoring output caninclude a detection of traffic on a channel. At 410, the communicationprocess determines a first transmission period for the first channel byapplying two or more inter-packet durations, such as Interframe Space(IFS) durations, to the monitoring output. An IFS duration can control aduration between two sequential frame transmissions. A frametransmission can include a packet transmission. Another IFS duration cancontrol a duration of a waiting period before a frame transmission. IFSdurations can have different lengths. Various examples of IFS durationsinclude an Arbitration IFS (AIFS) duration and a point coordinationfunction (PCF) IFS (PIFS) duration. In some implementations, when themonitoring output indicates a presence of traffic on the first channelduring a period based on the AIFS duration, the first transmissionperiod can be determined by an end of a PIFS duration. A period based onthe AIFS duration can include a back-off period. In someimplementations, when the monitoring output indicates a presence oftraffic on the first channel during a period based on the AIFS durationand a back-off period, a wireless device can freeze the back-off perioduntil the first channel becomes idle again.

At 415, the communication process determines a second transmissionperiod for the second channel by applying the two or more IFS durationsto the monitoring output. Applying an IFS duration can include startinga timer, which is resettable based on a detection of traffic. When themonitoring output indicates a presence of traffic on the second channelduring a period based on the AIFS duration, the second transmissionperiod can be determined by an end of a PIFS duration. To controlacknowledgement response(s), the end of the first transmission periodcan be aligned with the end of the second transmission period. Note thatthe starts of the first and second transmission periods can vary basedon a previous detection of traffic. In some cases, the starts of thefirst and second transmission periods are the same. In someimplementations, the communication process determines two or moretransmission periods by applying two or more IFS durations to themonitoring output.

At 420, the communication process transmits, based on the firsttransmission period, a first packet on the first channel to cause one ormore wireless communication devices to set a network allocation vectorfor the first channel and the second channel based on a reception of thefirst packet. At 425, the communication process transmits, based on thesecond transmission period, a second packet on the second channel. Insome implementations, the communication process controls transmissioncircuitry to transmit a packet.

At 430, the communication process monitors, after the end of the firsttransmission period, for one or more acknowledgements. The process caninclude sending information that indicates a scheduling ofacknowledgements for two or more devices.

In some cases, an access point can transmit packets to two devices forrespective overlapping transmission periods. The two devices can bebased on different respective wireless communication standards (e.g.,IEEE 802.11n or IEEE 802.11ac). For example, transmitting a first packetcan include transmitting to a first wireless communication device thatis configured for communications based on a first wireless communicationstandard (e.g., IEEE 802.11n), whereas, transmitting a second packet caninclude transmitting to a second wireless device that is configured forcommunications based on a second wireless communication standard (e.g.,IEEE 802.11ac). Note that the first and the second wirelesscommunication standards can define mutually compatible communications onthe first channel, with the second standard defining communications forthe first and second channels.

In some cases, an access point can have overlapping transmissions to thesame device using multiple channels. For example, transmitting first andsecond packets can include transmitting the packets concurrently to thesame device. These packets can form an aggregated packet that providesincreased communication bandwidth.

FIGS. 5A, 5B, 5C, and 5D show different examples of communication flowsvia multiple channels. These examples make use of primary channels P1and P2 and secondary channels S1 and S2. Note that a transmission on aprimary channel may include a concurrent transmission on a secondarychannel.

FIG. 5A shows an example of a communication flow that includestransmissions on multiple channels. To obtain a transmission opportunity(TXOP), a device such as an AP can monitor one or more primary channelsand one or more secondary channels for wireless traffic. If a primarychannel has been idled for an AIFS plus a back-off duration, and one ormore secondary channels have been idle for at least a PIFS duration, thedevice can used the idle channels for the TXOP. Based on obtaining aTXOP, the device can send one or more frames continuously with a SIFSduration gap between the frames. In this example, based on a durationcorresponding to an AIFS and a back-off parameter in the P1 channel anda duration of PIFS in the S1, P2, and S2 channels, an AP, in a TXOP,transmits a first packet 505 to a HT device on the P1 and S1 channels,and transmits a second packet 510 to a VHT device on the P2 and S2channels. The transmissions of the first packet 505 and the secondpacket 510 run concurrently. In the presence of traffic on a channel,the AP can wait a duration corresponding to a PIFS before transmitting apacket. The reception of the first packet 505 on the P1 channel sets aVirtual NAV (VNAV) period for the P1 and P2 channels, and associatedsecondary channels, on a client device. A packet 505, 510 can include adata unit such as a Physical Layer Protocol Data Unit (PPDU). In someimplementations, a packet 505, 510 can include multiple data units.

The AP device coordinates the transmission of the packets 505, 510 suchthat they end at the same time to create a window for acknowledgements(ACKs) such as a block acknowledgement (BA). Based on a durationcorresponding to a Short Interframe Space (SIFS), the HT device cantransmit one or more BAs 515 a, 515 b to the AP to acknowledge receptionof the first packet 505. Based on the end of the transmission of the BAs515 a, 515 b and another SIFS duration, the VHT device can transmit oneor more BAs 517 a, 517 b to the AP to acknowledge reception of thesecond packet 510. In some implementations, the AP device sends blockacknowledgement requests (BARs) to control the transmission of BAs fromtwo or more devices.

The AP can use the P1 and P2 channels and associated secondary channels.S1 and S2 to transmit data to one or more devices. In some cases, the APcan use the first packet 505 to transmit to a VHT device. Moreover, theAP can use the second packet 510 to transmit to the same or differentVHT device.

FIG. 5B shows another example of a communication flow that includestransmissions on multiple channels. In this example, receiving atransmission of a first packet 520 from a device on the P2 and S2channels delays a transmission of data on the P2 and S2 channels. Thetransmission of a first packet 520 sets a NAV. Based on an end of thefirst packet 520 and a PIFS duration, the AP transmits a third packet530 to a VHT device via the P2 and S2 channels. Based on an AIFS plusback-off duration, an AP transmits a second packet 525 to a HT devicevia the P1 and S1 channels. The second packet 525 can be indicative of aClear To Send (CTS) message. For example, the second packet 525 caninclude a CTS-to-self. In this example, a portion of the transmissionsof the second packet 525 and the third packet 530 overlap. Thetransmission of the second packet 525 on the P1 channel sets a VNAVperiod for the P1 and P2 channels and associated S1 and S2 channels.

The AP coordinates the transmission of the second packet 525 and thirdpacket 530 such that they end at the same time to create a window forACKs 540 a, 540 b from the HT device and ACKs 545 a, 545 b from the VHTdevice. The ACKs from the HT and VHT devices are allowed to overlap,albeit on different channels.

FIG. 5C shows another example of a communication flow that includestransmissions on multiple channels. In this example, receiving atransmission of a first packet 550 on P1 and S1 channels delays atransmission of data on the P1 channel. Based on the end of thetransmission of the first packet 550 and a PIFS duration, the APtransmits a second packet 555 to a HT device via the P1 and S1 channels.In some cases, the second packet 555 can include a CTS-to-self insteadof data for a device. The transmission of the second packet 555 on theP1 channel sets a transmission protection period such as a VNAV periodfor the P1 and P2 channels. The transmission of the second packet 555prevents devices, which are listening, from transmitting on the P1 andS1 channels. Based on an AIFS plus back-off duration, the AP transmits athird packet 560 to a VHT device via the P2 and S2 channels. Note thatthe start of the third packet 560 is earlier than the second packet 555due to the previous traffic.

The AP device coordinates the transmission of the second packet 555 andthird packet 560 such that they end at the same time to create a windowfor ACKs 565 a, 565 b, 565 c, 565 d from the HT and VHT devices. In someimplementations, the ACKs from the HT and VHT devices are allowed tooverlap, albeit on different channels.

FIG. 5D shows another example of a communication flow that includestransmissions on multiple channels and a period for a clear channelassessment. In this example, an AP performs a Clear Channel Assessment(CCA). Based on an end of the CCA 570 and a PIES duration, the APtransmits a first packet 575 to a HT device via the P1 and S1 channels,and transmits a second packet 580 to a VHT device via the P2 and S2channels. The transmissions of the first packet 575 and the secondpacket 580 run concurrently. The transmission of the first packet 575 onthe P1 channel sets a VNAV period for the P1 and P2 channels. The AP isnot required to receive during the transmission of the first packet 575on the P1 channel. The AP coordinates the transmission of the packets575, 580 such that they end at the same time to create a window foracknowledgements 585 a, 585 b,

FIG. 6 shows an example of a bandwidth indication for DL-OFDMA. An APcan announce support for downlink OFDMA (DL-OFDMA). During anassociation period with an AP, a VHT device can indicate support forDL-OFDMA. The AP can send a bandwidth indication to indicate bandwidthsfor respective channels associated with DL-OFDMA. A bandwidth indication605 includes bit values (B1-B4) for respective channels (C1-C4).Channels C1 and C2 can be grouped into a first segment and channels C3and C4 into a second segment. Channel C1 can be deemed the primarychannel and channels C2, C3 and C4 as secondary channels. A combinationof the bit values can indicate bandwidths for respective segments. Notethat the bandwidth for the first segment can be different than thebandwidth for the second segment. In some bit value combinations, nobandwidth is indicated.

With respect to the following figures, transmission signals can includeone or more legacy training fields (L-TFs) such as a Legacy ShortTraining Field (L-STF) or Legacy Long Training Field (L-LTF).Transmission signals can include one or more Legacy Signal Fields(L-SIGs). Transmission signals can include one or more HT Signal Fields(HT-SIGs). Transmission signals can include one or more HT trainingfields (HT-TFs). Examples of such training fields include a HT ShortTraining Field (HT-STF) and a HT Long Training Field (HT-LTF).Transmission signals can include one or more VHT Signal Fields(VHT-SIGs). Transmission signals can include one or more HT trainingfields (VHT-TFs). Examples of such training fields include a VHT ShortTraining Field (VHT-STF) and a VHT Long Training Field (VHT-LTF).Transmission signals can include different types of data fields such asHT-Data fields and VHT-Data fields. A packet that is indicated by atransmission can include training fields, signal fields, and a datacomponent, e.g., VHT data or HT data.

FIGS. 7A and 7B show examples of communication flow layouts, includingacknowledgement responses, based on Orthogonal Frequency-DivisionMultiple Access (OFDMA). In these examples, an AP concurrently transmitsHT data and VHT data. An AP can communicate with devices such as HTdevices and VHT devices.

FIG. 7A shows an example of a communication flow layout that includesconcurrent acknowledgement responses. An AP can use a primary channel totransmit to a HT device and a secondary channel to transmit to a VHTdevice. A HT transmission 705 can be 20 MHz or 40 MHz wide. A VHTtransmission 710 can be 40, 80, 120, or 160 MHz wide. A bandwidth fieldin a VHT-SIG-A 715 can indicate a bandwidth of the VHT transmission 710.In some implementations, a length field of the VHT-SIG-A 715 indicatesthe bandwidth.

If required, the AP can include padding 730 to align an end of the VHTtransmission 710 with an end of the HT transmission 705. A VHT devicecan use an identifier such as a device identifier or a group identifierto determine whether the VHT transmission 710 is intended for itself.The HT device responds with a HT-ACK 720 on the primary channel, whereasthe VHT device responds, concurrently, with a VHT-ACK 725 on thesecondary channel.

FIG. 7B shows an example of a communication flow layout that includessequential acknowledgement responses. An AP can use a primary channel totransmit to a HT device and a secondary channel to transmit to a VHTdevice. An HT transmission 750 can be 20 MHz or 40 MHz wide. A VHTtransmission 755 can be 40, 80, 120, or 160 MHz wide. A bandwidth fieldin a VHT-SIG-A 760 can indicate a bandwidth of the VHT transmission 755.A duration value in a MAC header 765 of the HT transmission 750indicates an end of a period (e.g., end of NAV) for acknowledgement(s)to the HT transmission 750 and the WIT transmission 755. An offset valuein a MAC header 767 of the VHT transmission 755 indicates an offsetvalue for a VHT device. The VHT device uses the offset value to base atransmission of one or more VHT-ACKs 770 a, 770 b so as to not overlapwith the HT-ACK 760. In this example, the HT-ACK 760 is only transmittedin a single subchannel, e.g., a 20 or 40 MHz subchannel. The BARs 765 a,765 b and the VHT-ACKs 770 a, 770 b are transmitted based on aduplication mode that replicates a response in multiple subchannels.

A VHT device can detect downlink OFDMA transmissions by processing areceived signal. For example, a length field (e.g., L_LENGTH) in a L-SIG761 a, 761 b can be used to signal a downlink OFDMA transmission to aVHT device. Downlink OFDMA signaling via the length field can bebackwards compatible with IEEE 802.11n. In IEEE 802.11n, L_LENGTH isdefined as

${L\_ LENGTH} = {{\left\lceil \frac{{TXTIME} - {Signal\_ Extention} - 20}{4} \right\rceil \times 3} - 3}$where TXTIME represents a transmission time and signal extensionrepresents a signal extension value. It is noted that this L_LENGTHmodulo three equals zero.

For a VHT device participating in a downlink OFDMA transmission,L_LENGTH can be defined as

${L\_ LENGTH} = {{\left\lceil \frac{{TXTIME} - {Signal\_ Extention} - 20}{4} \right\rceil \times 3} - 2.}$It is noted that this L_LENGTH modulo three equals one. In someimplementations, L_LENGTH can be defined as

${L\_ LENGTH} = {{\left\lceil \frac{{TXTIME} - {Signal\_ Extention} - 20}{4} \right\rceil \times 3} - 1}$to indicate a downlink OFDMA transmission. A VHT device receiving aL-SIG that indicates a IEEE 802.11n transmission (e.g., a rate of 6Mbps) and a L_LENGTH condition that indicate a downlink OFDMAtransmission. In some implementations, a L_LENGTH condition is when theL_LENGTH value modulo three equals one. In some implementations, theL_LENGTH condition is when the L_LENGTH value modulo three does notequal zero.

To process received transmission 750, 755, a VHT device can perform aFFT based on a bandwidth of 20, 40, 80, or 160 MHz. Based on a rotationon the first and second symbol of a HT-SIG 762 and a VHT-SIG-A 760, atransmission on a primary channel can be identified as a HT transmission750 and a transmission on one or more secondary channels can beidentified as a VHT transmission 755. The VHT device can use tonesassociated with the VHT transmission 755 to determine the receivedVHT-SIG-A 760 information and determine a channel bandwidth. The VHTdevice processes a received PPDU based on VHT-SIG information.

FIG. 8 shows an example of a communication flow layout for a primarychannel and four secondary channels. An AP can communicate with clientdevices via a primary channel, P channel 810, and secondary channels, S1channel 820 a, S2 channel 820 b, S3 channel 820 c, and S4 channel 820 d.A 40 MHz wide secondary channel 820 b can be split into two 20 MHz widesubchannels 825 a, 825 b (labeled S21 and S22). Based on detecting aDL-OFDMA transmission (e.g., detecting such a transmission via anindication in L-TF(s), L-SIG(s), or a prior packet), a VHT device startsto check the S21 subchannel 825 a for VHT packets. In someimplementations, the VHT device checks the S22 subchannel 825 b for VHTpackets. In some implementations, the VHT device checks a combination ofsubchannels 825 a, 825 b.

An AP can include information in its transmissions to differentiate anIEEE 802.11ac based downlink OFDMA transmission from other transmissionssuch as an IEEE 802.11a transmission, an IEEE 802.11n transmission, oran IEEE 802.11ac transmission to a single device. For an OFDMA packet, areceiving VHT device checks the channels carrying a VHT frame, whereasHT devices check the P, S1, or both channels for a HT frame. Forexample, a L-SIG with {rate=6 Mbps, and L_LENGTH %3≠0} in the P channel810 and a L-SIG with {rate=6 Mbps, and L_LENGTH %3≠0} in the S21 channel825 a can be used to indicate a DL-OFDMA transmission.

In some cases, a VHT device may decode a L-SIG in the P channel 810. AL-SIG with {rate=6 Mbps, and L_LENGTH %3≠0} can indicate a DL-OFDMAtransmission. If a non-HT PPDU uses {rate=6 Mbps, and L_LENGTH %3≠0}, aDL-OFDMA capable VHT device can store and check the following twosymbols in the P channel 810 and the S21 channel 825 a to determinewhether a received transmission includes a single non-HT packet or aDL-OFDMA transmission.

If a VHT device detects signaling information such as a L-STF, L-LTF, orL-SIG in the P channel 810 and the S21 channel 825 a at around the sametime, the VHT device can then check S21 channel 825 a for a L-SIG and aVHT-SIG-A. If present, the L-SIG, VHT-SIG-A, or both can indicatewhether the received transmission is a non-OFDMA frame (e.g., a framecontaining a packet for a single device) or a DL-OFDMA frame (e.g., aframe containing separate data for two or more devices). In someimplementations, when transmitting L-SIG on I-rail, a low power signaltransmitted on an unused Q-rail (e.g., at 6 dB lower than the power onI-rail) can be used to indicate a DL-OFDMA transmission. After a VHTdevice detects an OFDMA frame, the VHT device checks the VHT-SIG fieldin the S21 channel to determine the channels carrying the VHT frame andthe associated channel bandwidths.

FIG. 9 shows an example of a dual-primary channel structurearchitecture. An AP can communicate with client devices via a primarychannel (e.g., P channel 910) and one or more secondary channels (e.g.,S1 channel 920 a, S2 channel 920 b, S3 channel 920 c, and S4 channel 920d). The P channel 910 can be 20 MHz wide. A secondary channel 920 a thatis adjacent to the P channel 910 can be 20 MHz wide. Other secondarychannels 920 b, c, d can be 40 MHz wide. A 40 MHz wide secondary channel920 b can be split into two 20 MHz wide channels 925 a, 925 b (labeledS21 and S22), one of which can be deemed a primary.

The AP reserves a transmission opportunity (TXOP) period 905 forDL-OFDMA transmission by using an OFDMA control frame. The OFDMA controlframe indicates that the following TXOP is an OFDMA TXOP. In an OFDMATXOP, HT devices and IEEE 802.11a based devices can monitor the Pchannel 910 for channel activities, whereas VHT devices can monitor theS21 channel 925 a for channel activities. The presence of a VHT-SIG-A inthe S21 channel 925 a can indicate a transmission type (e.g., a DL-OFDMAtransmission type or a non-OFDMA transmission type) and subchannelusage. VHT-SIGs such as VHT-SIG-A or VHT-SIG-B can include OFDMAbandwidth usage for one or more VHT devices. For example, a VHT-SIG caninclude an OFDMA group identifier and bandwidth information such asbandwidth allocation values for one or more group members. Based on suchbandwidth information and the OFDMA group identifier, a VHT device canprepare to receive a transmission on the S21 and S22 channels, or, ifotherwise indicated, on all of the channels.

The AP can concurrently transmit a first transmission 915 a to a non-VHTdevice and second transmission 915 b to a VHT device. A non-VHT devicesuch as a HT device or an IEEE 802.11a based device can send an ACK 930following a data transmission 915 a, whereas a VHT device can send anacknowledgement such as a BA 950 following a transmission of a BAR 940that is subsequent to the ACK 930 from the non-VHT device. In thefuture, the AP can use the P channel 910 and all of the secondarychannels 920 a-d to transmit VHT Data 960 to a VHT device.

Wireless communication devices can provide CCA on a primary channel(e.g., P channel 910) and associated secondary channels (e.g., S1-S4channels 920 a-d). In some implementations, a receiver of a VHT devicewith an operating channel width set to 80/160 MHz can provide CCA onboth the primary and the secondary channels. When the secondary channelsare idle, the start of a valid 20 MHz HT/VHT signal in the primarychannel at a receive level equal to or greater than the minimummodulation and coding rate sensitivity of −82 dBm can cause the PHY toset a PHY CCA BUSY status for the primary channel with a probability ofgreater than 90% within four seconds.

The start of a valid 40 MHz HT or 40 MHz VHT signal that occupies boththe primary channel and the first secondary channel at a receive levelequal to or greater than the minimum modulation and coding ratesensitivity of −79 dBm can cause the PHY to set a PHY CCA BUSY statusfor both the primary channel and the first secondary channel with a perchannel probability of greater than 90% within four seconds.

The start of a valid 80 MHz VHT signal that occupies both the primarychannel and some or all of the secondary channels at a receive levelequal to or greater than the minimum modulation and coding ratesensitivity of −76 dBm can cause the PHY to set PHY CCA BUSY status forboth the primary channel and the first and second secondary channel witha per channel probability of greater than 90% within four seconds. Othervalues for the minimum modulation and coding rate sensitivity arepossible for different bandwidth configurations (e.g., −73 dBm for a 120MHz VHT signal, and −70 dBm for a 160 MHz VHT signal).

The receiver can hold a 20 MHz primary channel CCA signal busy for asignal at or above a predetermined threshold value (e.g., −62 dBm) inthe 20 MHz primary channel. This receive level is 20 dB above theminimum modulation and coding rate sensitivity for a 20 MHz PPDU. Whenthe primary channel is idle, the receiver can hold the 20 MHz secondarychannel CCA signal busy for a signal at or above the predeterminedthreshold value in the 20 MHz secondary channel. In someimplementations, when the primary channel is idle, the receiver can holda 40 MHz secondary channel CCA signal busy for a signal at or above thepredetermined threshold value in a 20 MHz subchannel of the 40 MHzsecondary channel. In some implementations, when the primary channel isidle, the receiver can hold a 80 MHz secondary channel CCA signal busyfor any signal at or above the predetermined threshold value in a 20 MHzsubchannel of the 80 MHz secondary channel.

The receiver can hold the 20 MHz primary channel CCA and one or moresecondary channels CCA busy for a signal present in the primary and oneor more secondary channels that is at or above the predeterminedthreshold value in the primary channel and at or above the predeterminedthreshold value in the one or more secondary channels. The receiver canhold the 20 MHz primary channel CCA signal busy for any signal at orabove the predetermined threshold value in the 20 MHz primary channel.This level is 20 dB above the minimum modulation and coding ratesensitivity for a 20 MHz PPDU. When the primary channel is idle, thereceiver can hold the 20 MHz secondary channel CCA signal busy for asignal at or above the predetermined threshold value in the 20 MHzsecondary channel. When the primary channel is idle, the receiver canhold a 40/80 MHz secondary channel CCA signal busy for a signal at orabove the predetermined threshold value in a 20 MHz subchannel of the40/80 MHz secondary channel. The receiver can hold the 20 MHz primarychannel CCA and one or more secondary channels CCA busy for a signalpresent in the primary and the secondary channel(s) that is at or abovethe predetermined threshold value in the primary channel and at or abovethe predetermined threshold value in the secondary channel(s).

A receiver that does not support the reception of HT-GF format PPDUs canhold the CCA signal busy (e.g., set a PHY CCA BUSY status) for a validHT-GF signal in the primary channel at a receive level equal to orgreater than −72 dBm when the first secondary channel is idle. Areceiver that does not support the reception of HT-GF format PPDUs canhold the 20 MHz primary channel CCA and the 20 MHz secondary channel CCAbusy (e.g., set a PHY CCA BUSY status) for a valid 40 MHz HT-GF signalin the primary and the first secondary channels at a receive level equalto or greater than −69 dBm. A receiver that does not support thereception of HT-GF format PPDUs can hold the CCA signal busy for a validHT-GF signal in the primary channel at a receive level equal to orgreater than −72 dBm when the first secondary channel is idle. Areceiver that does not support the reception of FIT-GF format PPDUs canhold both the 20 MHz primary channel CCA and the 20 MHz secondarychannel CCA busy for any valid 40 MHz HT-GF signal in both the primaryand the first secondary channel at a receive level equal to or greaterthan −69 dBm.

FIG. 10 shows an example of a layout of overlapping channelizations. Alayout 1005 of channels used by one or more wireless communicationsystems can include 80 MHz wide-hand channels (e.g., channels A, B, C,and D) and 160 MHz wide-band channels (e.g., channels E, F, and G). The80 MHz wide channels do not overlap with each other. Channel E overlapswith channels A and B. Channel F overlaps with channels C and D. ChannelG overlaps with channel E and F. A 80 MHz wide-band channel can includeone 20 MHz primary subchannel and multiple secondary subchannels. A 160MHz wide-band channel can include one 20 MHz primary subchannel andmultiple secondary subchannels. Beacons are transmitted in the primarysubchannel. When an AP establishes a BSS, the AP can be required not touse an OBSS's secondary channel as the AP's primary channel. When an APestablishes a BSS, the AP can be required not to use an OBSS's primarychannel or a 20 MHz only channel as the AP's secondary channel.

If an OBSS is present in channel E and channel F, and their associatedprimary channels fall into channel G, a new BSS may not be establishedin channel G. However, the AP controlling the BSS associated with G mayselect one of the OBSS's primary channels as its own primary channel.The AP of BSS G can access the secondary channel corresponding to theother primary channel(s) only after the AP's own primary channel is idlefor a duration of AIFS plus backoff and the corresponding secondarychannel is idle for at least the same duration.

If an OBSS is present in channel E and channel F, and all of channel G'ssubchannels are occupied as the secondary channels of OBSS E and F, anew BSS cannot be established in channel G. However, before selecting aprimary channel in channel G, the AP can scan channels G, E and F tocollect OBSS information, so as to not overlap the AP's primary channelwith an OBSS's secondary channel.

If channel F does not exist, an AP can scan channels E and G to collectOBSS information to select primary and secondary channels. In someimplementations, an AP can scan channel G, and if the AP cannot find anOBSS's primary channel in channel B, it selects a primary Channel inchannel C.

A few embodiments have been described in detail above, and variousmodifications are possible. The disclosed subject matter, including thefunctional operations described in this specification, can beimplemented in electronic circuitry, computer hardware, firmware,software, or in combinations of them, such as the structural meansdisclosed in this specification and structural equivalents thereof,including potentially a program operable to cause one or more dataprocessing apparatus to perform the operations described (such as aprogram encoded in a computer-readable medium, which can be a memorydevice, a storage device, a machine-readable storage substrate, or otherphysical, machine-readable medium, or a combination of one or more ofthem).

The term “data processing apparatus” encompasses all apparatus, devices,and machines for processing data, including by way of example aprogrammable processor, a computer, or multiple processors or computers.The apparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

A program (also known as a computer program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astand alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A program does notnecessarily correspond to a file in a file system. A program can bestored in a portion of a file that holds other programs or data (e.g.,one or more scripts stored in a markup language document), in a singlefile dedicated to the program in question, or in multiple coordinatedfiles (e.g., files that store one or more modules, sub programs, orportions of code). A program can be deployed to be executed on onecomputer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of what may be claimed, but ratheras descriptions of features that may be specific to particularembodiments. Certain features that are described in this specificationin the context of separate embodiments can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments.

Other embodiments fall within the scope of the following claims.

1. A method comprising: monitoring wireless communication channels,including a first channel and a second channel, to produce a monitoringoutput; determining a first transmission period for the first channel byapplying a first Interframe Space (IFS) duration and a second IFSduration to the monitoring output, wherein the second duration isshorter than the first duration; determining a second transmissionperiod for the second channel by applying the first IFS duration and thesecond IFS duration to the monitoring output, wherein an end of thesecond transmission period is aligned with an end of the firsttransmission period; transmitting, based on the first transmissionperiod, a first packet on the first channel to cause one or morewireless communication devices to set a transmission protection periodfor the first channel and the second channel based on a reception of thefirst packet; transmitting, based on the second transmission period, asecond packet on the second channel; and monitoring, after the end ofthe first transmission period, for one or more acknowledgements.
 2. Themethod of claim 1, wherein: the first duration is an Arbitration IFS(AIFS) duration; the second duration is a Point Coordination FunctionIFS (PIFS) duration; and monitoring the channels comprises monitoringfor wireless traffic on the wireless communication channels with respectto the first duration and the second duration.
 3. The method of claim 2,wherein determining the first transmission period comprises, in responseto the monitoring output indicating a presence of traffic on the firstchannel during a period based on the AIFS duration, determining thefirst transmission period based on an end of the PIFS duration.
 4. Themethod of claim 2, wherein determining the second transmission periodcomprises, in response to the monitoring output indicating a presence oftraffic on the second channel during a period based on the AIFSduration, determining the second transmission period based on an end ofthe PIFS duration.
 5. The method of claim 1, wherein: transmitting thefirst packet comprises transmitting to a first wireless communicationdevice that is configured for communications based on a first wirelesscommunication standard; and transmitting the second packet comprisestransmitting to a second wireless device that is configured forcommunications based on a second wireless communication standard,wherein the first channel is used by each of the first wirelesscommunication standard and the second wireless communication standard.6. The method of claim 5, wherein: the first packet comprises a fieldindicative of a length of the first packet; and the method furthercomprises setting the field to indicate a downlink OrthogonalFrequency-Division Multiple Access transmission.
 7. The method of claim1, wherein: transmitting the first packet comprises transmitting to awireless communication device; transmitting the second packet comprisestransmitting to the wireless communication device; and the wirelesscommunication channels are associated with an overlapping basic serviceset (OBSS) configured for communications based on 80 MHz, 120 MHz, or160 MHz bandwidths.
 8. An apparatus comprising: circuitry to accesswireless communication channels, including a first channel and a secondchannel; and processor electronics configured to monitor the wirelesscommunication channels to produce a monitoring output, determine a firsttransmission period for the first channel by applying a first InterframeSpace (IFS) duration and a second IFS duration to the monitoring output,wherein the second duration is shorter than the first duration,determine a second transmission period for the second channel byapplying the first IFS duration and the second IFS duration to themonitoring output, wherein an end of the second transmission period isaligned with an end of the first transmission period, control atransmission, based on the first transmission period, of a first packeton the first channel to cause one or more wireless communication devicesto set a transmission protection period for the first channel and thesecond channel based on a reception of the first packet, control atransmission, based on the second transmission period, a second packeton the second channel, and monitor, after the end of the firsttransmission period, for one or more acknowledgements.
 9. The apparatusof claim 8, wherein: the first duration is an Arbitration IFS (AIFS)duration; the second duration is a Point Coordination Function IFS(PIFS) duration; and the processor electronics are configured to monitorfor wireless traffic on the wireless communication channels with respectto the first duration and the second duration.
 10. The apparatus ofclaim 9, wherein the processor electronics, in response to themonitoring output indicating a presence of traffic on the first channelduring a period based on the AIFS duration, are configured to determinethe first transmission period based on an end of the PIFS duration. 11.The apparatus of claim 9, wherein the processor electronics, in responseto the monitoring output indicating a presence of traffic on the secondchannel during a period based on the AIFS duration, are configured todetermine the second transmission period based on an end of the PIFSduration.
 12. The apparatus of claim 8, wherein: the first packet istransmitted to a first wireless communication device that is configuredfor communications based on a first wireless communication standard; andthe second packet is transmitted to a second wireless device that isconfigured for communications based on a second wireless communicationstandard, wherein the first channel is used by each of the firstwireless communication standard and the second wireless communicationstandard.
 13. The apparatus of claim 12, wherein: the first packetcomprises a field indicative of a length of the first packet; and theprocessor electronics are configured to set the field to indicate adownlink Orthogonal Frequency-Division Multiple Access transmission. 14.The apparatus of claim 8, wherein: the first packet and the secondpacket are transmitted to the same wireless communication device, andthe wireless communication channels are associated with an overlappingbasic service set (OBSS) configured for communications based on 80 MHz,120 MHz, or 160 MHz bandwidths.
 15. A system comprising: circuitry totransmit and receive on wireless communication channels, including afirst channel and a second channel; and processor electronics configuredto monitor the wireless communication channels to produce a monitoringoutput, determine a first transmission period for the first channel byapplying a first Interframe Space (IFS) duration and a second IFSduration to the monitoring output, wherein the second duration isshorter than the first duration, determine a second transmission periodfor the second channel by applying the first IFS duration and the secondIFS duration to the monitoring output, wherein an end of the secondtransmission period is aligned with an end of the first transmissionperiod, control a transmission, based on the first transmission period,of a first packet on the first channel to cause one or more wirelesscommunication devices to set a transmission protection period for thefirst channel and the second channel based on a reception of the firstpacket, control a transmission, based on the second transmission period,a second packet on the second channel, and monitor, after the end of thefirst transmission period, for one or more acknowledgements.
 16. Thesystem of claim 15, wherein: the first duration is an Arbitration IFS(AIFS) duration; the second duration is a Point Coordination FunctionIFS (PIFS) duration; and the processor electronics are configured tomonitor for wireless traffic on the wireless communication channels withrespect to the first duration and the second duration.
 17. The system ofclaim 16, wherein the processor electronics, in response to themonitoring output indicating a presence of traffic on the first channelduring a period based on the AIFS duration, are configured to determinethe first transmission period based on an end of the PIFS duration. 18.The system of claim 16, wherein the processor electronics, in responseto the monitoring output indicating a presence of traffic on the secondchannel during a period based on the AIFS duration, are configured todetermine the second transmission period based on an end of the PIFSduration.
 19. The system of claim 15, wherein: the first packet istransmitted to a first wireless communication device that is configuredfor communications based on a first wireless communication standard; andthe second packet is transmitted to a second wireless device that isconfigured for communications based on a second wireless communicationstandard, wherein the first channel is used by each of the firstwireless communication standard and the second wireless communicationstandard.
 20. The system of claim 19, wherein: the first packetcomprises a field indicative of a length of the first packet; and theprocessor electronics are configured to set the field to indicate adownlink Orthogonal Frequency-Division Multiple Access transmission. 21.The system of claim 15, wherein: the first packet and the second packetare transmitted to the same wireless communication device, and thewireless communication channels are associated with an overlapping basicservice set (OBSS) configured for communications based on 80 MHz, 120MHz, or 160 MHz bandwidths.